Communication between a transmitter and a receiver is only effective within a predetermined radius R. When data communication is required between moving participants each of whom is provided with a suitable transmitter and receiver, each participant would receive data transmitted by any other participant within a radius R thereof unless, of course, steps were taken to prevent this. Whilst it is possible to allocate different transmission frequencies to each of the participants, this is not feasible when completely reciprocal data communication is required between all of the participants. Such reciprocal data communication is a requirement, for example, in military aircraft where a limited number of pilots must be able to maintain contact with other friendly pilots all of whom must, therefore, transmit and receive data at the same frequency.
In such data communication, it is clearly an imperative that a pilot receive data from only one transmitter at any given time in order to avoid the confusion which would result from more than one transmission being received simultaneously. At its simplest, this desideratum can always be achieved by allocating time slices to each of the participants so that only one can transmit during any given time slice. According to such an approach, each participant transmits data during his time slice only and all participants within a radius R of the transmitting participant will receive the transmitted data.
However, although simple, such an approach is inefficient because it prohibits a participant from transmitting data, other than during his allotted time slice, even if there is absolutely no danger of a receiver receiving two such transmissions simultaneously. Put another way, if a participant A wishes to transmit data to his neighbor B at the same time as another participant C wishes to transmit data to his neighbor D, even if A and B on the one hand and C and D on the other hand, are so far apart that there would be no danger of A or B receiving C's transmission or of C or D receiving A's transmission, C is prevented from transmitting during A's time slice and, of course vice versa.
It would clearly be desirable to effect the desired data communication in accordance with a method that would take into consideration the mutual separation between the participants. However, bearing in mind that all of the participants are moving with respect to each other and, in the particular case of fighter aircraft are moving at very high speeds indeed, this is clearly no easy task.